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Projected changes in hydrologic niches of riparian plants in response to climate change
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Riparian zones are species-rich habitats also subject to wide-spread degradation and modification. The extensive habitat and biodiversity losses make conservation of riverine ecosystems a priority, especially in the few river systems that remain free-flowing. However, riparian ecosystems might also be threatened by ongoing and anticipated climate change. Models predict large changes in flow regime across the world, which is anticipated to alter riparian communities, but how is poorly known. In northern Europe, lower annual spring flood peaks and higher winter flows are expected, resulting in narrower riparian zones. To determine the impact on riparian plant species we surveyed five sites along the free-flowing Vindel River in northern Sweden. We calculated the probability of occurrence of plant species along gradients of flood frequency and duration. We then compared present and predicted future water-level fluctuations (based on climate models and IPCC emission scenarios) and thereby got an estimate of the future extent of the species based on their hydrologic requirements. The majority of the riparian species are predicted to decrease in elevational extent by on average 13−28 % until the end of the century, depending on scenario. Species growing in the upper, spring-flood controlled part of the riparian zone are predicted to decrease most, with largest reductions in species with narrow flood duration ranges (decreases of up to 54%). Many species would become less frequent than today, with stochastic extinctions expected along some reaches. Reductions may be more dramatic along rivers in the southern boreal zone where snowmelt-fed hydrographs are expected to be largely replaced by rain-fed ones. With few rivers remaining unaffected by dams and other human stressors, even moderate reductions in abundance can have grave consequences for regional conservation, calling for monitoring to detect declining species and management actions to minimize species losses. Management might include protection of more riverine ecosystems, reduction of negative impacts from land-use activities, implementation of more environmentally friendly flows, channel restoration, and more artificial management options such as mowing riparian meadows no longer maintained by recurrent floods.

Keyword [en]
climate change, flooding, niche width, probability curves, river banks, water table, inundation duration
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-43809OAI: oai:DiVA.org:umu-43809DiVA: diva2:416075
Available from: 2011-05-10 Created: 2011-05-10 Last updated: 2011-05-11
In thesis
1. Effects of climate change on boreal wetland and riparian vegetation
Open this publication in new window or tab >>Effects of climate change on boreal wetland and riparian vegetation
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Models of climate change predict that temperature will increase during the 21th century and the largest warming will take place at high northern latitudes. In addition to warming, predictions for northern Europe include increased annual precipitation and a higher proportion of the precipitation during winter falling as rain instead of snow. These changes will substantially alter the hydrology of rivers and streams and change the conditions for riverine communities. The warming is also expected to result in species adjusting their geographic ranges to stay within their climatic tolerances. Riparian zones and wetlands are areas where excess water determines the community composition. It is therefore likely that these systems will be highly responsive to alterations in precipitation and temperature patterns.

In this thesis we have tested the predicted responses of riparian vegetation to climate-driven hydrologic change with a six year long transplant experiment (I). Turfs of vegetation were moved to a new elevation with shorter or longer flood durations. The results demonstrate that riparian species will respond to hydrologic changes, and that without rare events such as unusually large floods or droughts, full adjustment to the new hydrological regime may take at least 10 years.

Moreover, we quantified potential effects of a changed hydrology on riparian plant species richness (II) and individual species responses (III) under different climate scenarios along the Vindel River in northern Sweden. Despite relatively small changes in hydrology, the results imply that many species will become less frequent than today, with stochastic extinctions along some reaches. Climate change may threaten riparian vegetation along some of the last pristine or near-natural river ecosystems in Europe. More extensive loss of species than predicted for the Vindel River is expected along rivers in the southern boreal zone, where snow-melt fed hydrographs are expected to be largely replaced by rain-fed ones.

With a seed sowing experiment, we tested the differences in invasibility between open wetlands, forested wetlands and riparian zones (IV). All six species introduced were able to germinate and survive in all habitats and disturbance levels, indicating that the tested wetlands are generally invisible. Germination was highest in open wetlands and riparian zones. Increasing seed sowing density increased invasion success, but the disturbance treatments had little effect. The fact that seeds germinated and survived for 2 to 3 years in all wetland habitats indicates that wetland species with sufficiently high dispersal capacity and propagule pressure would be able to germinate and establish here in their respective wetland type.

Our results clearly demonstrate that a changed climate will result in substantial changes to functioning, structure and diversity of boreal wetland and riparian ecosystems. To preserve species rich habitats still unaffected by dams and other human stressors, additional protection and management actions may have to be considered.

Place, publisher, year, edition, pages
Institutionen för ekologi, miljö och geovetenskap, Department of Ecology and Environmental Sciences, 2011. 30 p.
Keyword
biomass, flooding, hydrologic niche, invasibility, riparian zone, riparian plant species, river margin, climate scenario, seed sowing experiment, species composition, species richness, transplant experiment
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-43811 (URN)978-91-7459-184-2 (ISBN)
Public defence
2011-06-10, Älgsalen, Uminova Science Park, Tvistevägen 48, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2011-05-13 Created: 2011-05-10 Last updated: 2014-12-22Bibliographically approved

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